Coccolithophores are one of the most spectacular calcifying microalgae. They are the third most prominent group of phytoplankton with over 300 extant species, each of which displays a unique calcium carbonate cell covering. While the calcareous skeletons otherwise known as coccoliths, have attracted the attention of scientists from diverse fields, information relating to the function and molecular complexity of the underlying biomineralization processes is lacking. The manner in which macromolecules, in particular proteins, orchestrate the crystal growth processes and dictate the nanoscale architecture of the coccoliths is not known. Hence, the broad and long term objective of our laboratory is to understand the molecular underpinnings of biomineralization and the nanoscale shape and patterning of the calcite plates characteristic of marine coccolithophores. The major hypothesis underlying this research is that the design principles governing the synthesis of coccoliths can only be determined by identifying and characterizing the genes and gene products involved in their synthesis and assembly. Emiliania huxleyi (E. huxleyi) is recognized as the model coccolithophore because of its abundance, cosmopolitan distribution, and the ease with which it can be cultured. Its genome was recently sequenced in a collaborative effort between our laboratory and the U.S. Department of Energy, making it feasible to apply various global approaches to explore biomineralization. We propose herein to dissect biomineralization and the regulatory mechanisms required to coordinate this complex process by applying a comparative transcriptomics approach. To this end, we proposed to 1) use high throughput 454 sequencing to interrogate the transcriptome of three sister species (two calcifying and one non-calcifying) under nutrient conditions known to affect biomineralization, and 2) to identify cis-regulatory elements by examining the promoter sequences of functionally related sets of genes deemed critical to the calcification processes. This work will afford a robust and complete view of the biomineralization transcriptome and potential cis-acting regulatory elements. As a collaborative effort that relies on expertise in microbiology, genomics and molecular cell biology, bioinformatics and computational biology, this proposal promises to provide a valuable resource for scientists working to understand the regulation and control of biomineralization in this important model system.